Mix, in a bowl using a whisk:

1 egg
1 cup ice water

Sift together:

1 C flour
1 t baking powder
1 t sugar
1/2 c corn starch
1 t salt

Add dry ingredients to ice water and egg using whisk. Mix until very smooth. Fish or vegetables can be used with this batter. Zucchini and onion rings work very well. Dip in very cold batter and fry in 1" cooking oil.

Source: Margaret Glass